1. Field of the Invention
The present invention relates to a method for operation of a power generation plant.
2. Description of Related Art
An air storage turbine has been disclosed in DE 28 22 575. At times when the power consumption is low, for example at night and at weekends, a compressor acting as a power consuming machine uses electricity that is generated by basic load power stations to pump air into a storage volume, for example an underground cavern in a salt mine. The cavern is charged, for example, to 100 bar. At times when the electricity demand is high or if another power station fails, the stored air is used to drive an air turbine or a combined air/gas turbine, which generates electrical power via a generator. This significantly lengthens the operating life of basic load power stations and, in liberalized electricity markets, the peak power that can be generated in this way allows a considerable financial saving to be achieved. Furthermore, in liberalized electricity markets, the process of covering transient power demands, such as those which occur when a major load is switched on but especially when a major power station block fails, is highly lucrative. Even the pure provision of appropriate capacities can save a very large amount of money. When power generating plants fail, the capability for frequency support is in demand. During the first fractions of a second after the failure of an electricity supply, the grid frequency can be kept within the permissible tolerance without any further problems in a large grid by virtue of the rotating masses of the remaining power stations. However, after this, power reserves must be available immediately in order to prevent the frequency from decreasing, and thus prevent failure of the entire grid. Steam power stations which are operated slightly throttled back can provide power amounting to the order of magnitude of around 5% of their maximum power very quickly; however, they require several tens of minutes for power increases beyond this, for example up to 30% of their maximum power. When a major load is connected to the grid, load ramps are demanded from the power stations, in which the provision of a considerable amount of additional power is demanded in a time period in the region of seconds or up to ten minutes. Gas turbine plants and combination plants allow such increases to be coped with within minutes. An air turbine or combined air/gas turbine in a storage power station of the cited type has a comparable reaction. It is also known from operating experience that rapid load changes such as these cause severe temperature gradients and, associated with them, damaging thermal alternating loads and mechanical stresses particularly in the hot gas path (which is already thermally highly loaded in any case) of gas turbine groups or in the steam generators for steam and combination power stations. Geodetic hydroelectric power stations are admittedly able to mobilize significant power reserves within seconds; however, their availability is, of course, restricted.